1. Field of the Invention
The present invention relates to a printing apparatus, and, more particularly to a wet-type printing apparatus having a cleaner that is used for cleaning residual toner particles after transferring an image developed by using a liquid developer containing a carrier solution and toner particles.
2. Related Art
Printing apparatuses such as electronic photograph recording apparatuses and electrostatic recording apparatuses are classified into those of a dry-type and a wet-type. The printing apparatuses of the wet-type which use a liquid developer have advantages that cannot be achieved by those of the dry-type, and in recent years, its advantages have been re-confirmed.
The advantages of the wet-type printing apparatus over the dry-type printing apparatus are explained as follows:
1) The application of a liquid developer makes it possible to use very fine toner particles in the order of sub-micron size, and consequently to achieve high-quality images.
2) Since a high-density image is obtained by using only a small amount of toner, it is advantageous from the viewpoint of costs, and it is also possible to realize image quality as good as that obtained through an offset printing process or other like printing process.
3) Since the toner is fixed onto paper at comparatively low temperatures, it is possible to save energy.
However, some of inherent problems with the wet-type printing apparatus have been left unsolved, and for this reason, in the technical field of conventional printing apparatuses, the dry-type printing apparatuses have monopolized the market for a long time. One of the unsolved problems relates to cleaning means, and, more specifically, lies in the fact that a cleaning process for residual toner after a transferring process is more difficult than that of the dry-type printing apparatus.
The particle size of toner particles used in the liquid developer ranges approximately from 0.1 micron to 3 microns, which is smaller than the size of dry-type toner particles. For this reason, in an attempt to apply a cleaning system having scraping blades used in the dry-type printing apparatus to the wet-type printing apparatus, an insufficient cleaning process causing black lines, etc., tends to occur. In order to prevent this from occurring, it is necessary to make the scraping precision of the blades higher. However, it is difficult to achieve this from the practical point of view, and it is also difficult to maintain such high precision.
Under the above circumstances, in the cleaning device of the conventional wet-type printing apparatus, a method has been proposed, in which a great amount of liquid solvent is supplied to the residual toner after a transferring process to allow the toner particles to disperse in the liquid solvent so that the toner is removed together with the liquid solvent by using a roller or a blade (ref. Japanese Examined Patent Publication No. 63-4117). However, in this method, complicated mechanisms are required for supplying and recovering the liquid solvent, which causes the problems of a bulky cleaning device, frequent occurrences of troubles, and high production costs.
As described above, in the conventional printing apparatus using a liquid developer, the attempt to properly clean the residual toner after a transferring process results in problems of difficulty in practical use, complex and bulky devices and increased causes of troubles.
With these problems in mind, therefore, it is the primary object of the present invention to provide a novel printing apparatus using a liquid developer, in which a cleaning of residual toner after a transferring process is completely carried out to keep the surface of an image holding member in a good condition and to form an image with high image quality.
In order to achieve the above-mentioned object, a printing apparatus for printing an image onto a print medium with use of a liquid developer which contains a liquid carrier and a toner being dispersed in the liquid carrier, according to an aspect of the present invention comprises; an image holding member having an imaging surface on which a latent image corresponding to the image to be printed is generated; a development unit which provides the liquid developer to the imaging surface to form a toner image corresponding to the latent image: a transfer member which transfers the toner image from the imaging surface to the print medium; and a fibrous wipe member having a cleaning face contacting with the imaging surface for wiping a residual toner failing to be transferred from the imaging surface, by moving relatively to the imaging surface in a first direction, wherein the cleaning face comprises fibers having a directional distribution which is biassed to a second direction perpendicular to said first direction.